#7785 HIGH 9.1.0: unreliable ethernet connection

Zarro Boogs per Child bugtracker at laptop.org
Thu Aug 14 23:47:16 EDT 2008

#7785: unreliable ethernet connection
   Reporter:  AlbertCahalan  |       Owner:               
       Type:  defect         |      Status:  new          
   Priority:  high           |   Milestone:  9.1.0        
  Component:  not assigned   |     Version:  not specified
 Resolution:                 |    Keywords:               
Next_action:  never set      |    Verified:  0            
  Blockedby:                 |    Blocking:               

Comment(by AlbertCahalan):

 Replying to [comment:5 gregorio]:

 > A few more question on this particular bug: are you saying that any
 interruption of signal on the wire brings the connection down? e.g. if I
 unplug the wire then plug it back in 3 seconds later.

 I think "yes" if either:

 a. the DHCP server is giving out leases that are shorter than 3 seconds

 b. you get unlucky, with the lease expiring while the wire is unplugged

 DHCP lease times will vary by many orders of magnitude. Probably almost
 all lengths will be from 15 minutes to 1 month. Length is determined by
 local policy, often based on expectations of computer movement and
 sometimes based on the number of addresses remaining.

 > When does the XO pick a "bogus IP"? I think we only go out to dhcp at
 startup. Once you have an IP and are on the network, is there any time
 when you would need to contact the dhcp server again?

 You must contact the DHCP server before your lease expires. This is why
 the DHCP client must run as a daemon.

 > Did you find any other specific cases beyond the trouble connecting to
 the dhcp server?
 > How do we reproduce this problem? How do you know that the wireless
 didn't connect, find a dhcp server and get the IP address that way?

 I checked with the ifconfig command, as root. The USB-to-ethernet device
 got a bogus address. A DHCP server over wireless would not (must not...)
 affect other devices. Also, no reasonable DHCP server would give out such
 an address.

 To reproduce, boot the laptop with ethernet. Ask your sysadmin to tell you
 the length of your DHCP leases. Cut your connection until that amount of
 time has passed.

 > How slow was the dhcp server? How do you know it was slow? Did you get
 an IP address and a default gateway from DHCP (anything else)?

 Typically the server itself is not at fault; something happens to the
 physical connection. For example, the power adapter to my ethernet switch
 might fall out of the wall socket. This could go unnoticed for some time
 if the laptop is not being used for web browsing, etc.

 > If this is just a suggestion then there's no need to spend a lot of time
 on it. If there's a failure case for USB -> Ethernet connections we
 probably can't hold up this release for it unless it fatal in a large
 fraction of cases. If this problem also affects the wireless connections
 and there are a significant number of cases then we would consider it for
 blocker status.

 I have had a few wireless problems that could have been caused by this,
 but I did not think to check with the ifconfig command.

Ticket URL: <http://dev.laptop.org/ticket/7785#comment:8>
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